I've been meaning to start this thread for a little while now, but exactly what it says on the tin.
Anyshoe, "Arthur Goes to Camp" was the first episode I ever saw, even though it wasn't the full episode: this was back in the spring of 1998, back when my PBS didn't play the show regularly (that wouldn't eventually happen until late 2000), and I had a tape recording some PBS shows for me while I was in school, and towards the end of that specific recording was the beginning of "Arthur Goes to Camp" (the recording stopped on the bus as Sue Ellen looks out the window and asks, "Is that our camp?") Later that summer, both "Binky Barnes, Art Expert; Arthur's Lucky Pencil" and "Sue Ellen's Lost Diary; Arthur's Knee" came on, so I decided to tape them as well, because I remembered liking what I saw (and because I enjoyed the books when I was even younger).
Usually, Arthur was reserved for pledge drives, but occasionally, they would air an episode at random, it wasn't until after the summer pledge drive of 2000 that Arthur was added to the regular lineup at 4:30 in the afternoon (later bumped up to 4:00 a few years back).